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  1. #1
    Join Date
    Jul 2012
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    1

    Default The proper "grit" for pre paint sanding

    I recently had a painter say to me that using the wrong grit on bare wood can release oils in the wood that make it more difficult for paint to adhere. Thus my question would be, what is the proper grit for different scenarios? E.g. - new bare wood, stripped wood, high gloss layers on old wood, on metal, etc.

    I have an old Queen Anne that is in a constant state of remodel. I'm tackling new bare wood baseboard, high gloss trim and doors (with lead most certainly present), and various metal products.

    I would love to not have to completely reprime the high gloss doors. I was hoping to be able to oil prime the scratches and dings and latex the rest, but did have bad luck with a latex application on other trim.

    I am currently using a Sherwin Williams oil based primer, and usually Sherwin latexes, though I do love close to Home Depot and have access to. A Benjamin Moore.

    Thanks!

  2. #2
    Join Date
    Feb 2012
    Location
    Tacoma WA
    Posts
    87

    Default Re: The proper "grit" for pre paint sanding

    This is a new one on me, I have never heard of releasing oils by using the wrong sand paper. If you use to fine of grit, finer than 220, you could carmelize the sugars in the wood. This would not allow the paint to properly stick. New wood needs to be sanded to remove the carmeled sugars, start with 80 grit and work your way to 220. On the painted suface, check to see if it is oil based paint. Use 409, Fantastic or Goof Off 2, (waterbased), spray a little on the surface, let it sit for 5 minutes. Wipe it off, if it feels sticky when you wipe, it is water based paint. If it feels smooth, it is oil based paint. Oil based paint use 220 to do a light sand and wipe it down with a tsp substitute. If water based paint, use 220 and wipe down with a tack cloth. SW has a great paint for trim and doors, Pro Classic. I love the water based version, but it is very pricey. If you spray it, go light and 2 coats. If you brush it, water it down a little bit. It is to thick, but it has self levelers in it and it will run on you. Hope this helps, good luck.

  3. #3
    Join Date
    Aug 2007
    Posts
    6,612

    Default Re: The proper "grit" for pre paint sanding

    There are types of wood that are high in resin content that make them problematic for painting, but I've never heard of sanding "releasing oils".

    Pine is high in pitch, which is difficult to seal and stain or paint. Teak is also high in natural resins that can be hard to deal with, but it is unlikely that you've got teak in your Queen Anne.

    Tacoma lists several good steps for determining paint type and prep. I would not suggest spot priming and opt for full prime coat (two if necessary ) followed by two coats of paint. The problem with spot priming is the it will leave a different sheen under the paint which will affect the overall look once the item is completely repainted, producing "shiners". With a full, even coat of primer, you not only stand a better chance of the paint adhering to old surfaces, you have a good base to work from that will result in a more even top coat.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  4. #4
    Join Date
    Jan 2010
    Location
    Northern Virginia
    Posts
    1,001

    Default Re: The proper "grit" for pre paint sanding

    I have found that the right type of sandpaper makes a difference. Get abrasives specifically for paint work, not wood work.
    something like this:
    http://www.woodworkingshop.com/product/bx13592/
    Casey
    Remove not the ancient landmark, which your fathers have set.

  5. #5
    Join Date
    Feb 2012
    Location
    Tacoma WA
    Posts
    87

    Default Re: The proper "grit" for pre paint sanding

    A. Spruce is absolutely right about the shiners with spot priming. I have a few in my hallway. This was a combination of sanding the MDF at the joints and spot priming. Should you choose to use high gloss paint this is unlikely to happen, but it shows ever imprefection in the wood, paint and joints. The lower the sheen the greater the chance of these shiners showing up. Since I spray, I always do a full oil prime, everything is already masked. This cuts down prep time, gives best adhesion and blocks any stains from bleeding through. Spraying also gives the best looking paint job on trim and doors. Assumimg that you know how to spray the product you are using. Water based paints made for trim work are very touchy to use. This is because they have self levelers in them and they run very easily. I do not recommend oil based paint, not primer, for several reasons. One is that they yellow, two, recoat time is 1 day, three, if you have a run or drip, trying to sand it is very difficult unless you wait 30 days for it to cure. Good Luck and I hope this helps

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